The present invention relates to a vehicle pneumatics overpressure regulating circuit. This circuit is used to supply a pneumatic consumer of a vehicle with an operating pressure, the consumer being disposed in an interior. The interior is the passenger compartment. The overpressure regulating circuit has a compressed air source, which furnishes compressed air for the consumer. The overpressure regulating circuit also has a pressure switch, by means of which the compressed air source is turned on or off to supply the compressed air, and also has a supply line by way of which compressed air from the compressed air source can be carried to the consumer.
Until now, to supply pneumatic consumers in an interior of a vehicle, pressure switch assemblies were used in which either the pressure switch is disposed immediately downstream of the compressor, or the pressure switch is located directly on the consumer.
The vehicle pneumatics overpressure regulating circuit makes it possible for the pressure switch to be switched extremely precisely, by means of a disposition of a pneumatic measurement line that is separate from a supply line. As a result, the switch is independent of line segments or throttles disposed downstream of a compressed air source. While these otherwise lead to the buildup of a head pressure, as a result of which a pressure switch point at a pressure switch is reached, which is located earlier than without these line segments or throttles, the measurement line assures a direct measurement of the consumer, so that variations, of the kind that otherwise are caused by an engine or pump characteristic curve and a temperature of the compressed air in the supply line, do not occur. The proposed arrangement is also distinguished in that it is extremely robust, since the measurement line is independent of the supply line. This robustness, which is also due to the fact that the pressure switch is not exposed to dirt and weathering, is also exploited by the proposed method for operating a vehicle pneumatics overpressure regulating circuit of a pneumatic consumer, which can be accommodated in the engine compartment as well, for instance in the form of a pneumatic actuator with triggering via an electromagnet valve, in a vehicle and in particular in its interior. Thus such pneumatic consumers as central locking control elements and inflatable compartments in seat cushions and/or back rests in the vehicle can be controlled and regulated very precisely with regard to their demand for compressed air.
An especially advantageous feature provides that the compressed air source, in particular an air compressor, such as a vane cell or diaphragm pump, and the pressure switch itself are both placed in a common housing. In this way it is successfully possible to assure a compact construction, which makes a separation from the consumer possible. This is reinforced on the one hand by interchangeability of all of these components and by reduced expense for necessary sound damping means. The pneumatically operated elements are located in the sole housing, so that only this housing has to be provided with an appropriate sound damping means. This sound damping means in particular involves only slight expense whenever the consumer is located at an acoustically exposed place, while the housing with the components is disposed separately and at a distance from it.
It is also expedient if the pressure switch and the compressed air source or a tripping means for the compressed air source are connected to an electronic control unit with safety functions, in particular leak detection. That is, the compressed air source (pump), after a programmed running time during which the pressure-dictated shutoff point is not reached has been exceeded, is shut off (leakage or pump malfunction). The pressure switch, such as a mechanical pressure switch, has a turn-on and turn-off point, which in particular is adjustable. These switching points are evaluated as electrical signals by an electronic trigger means for the compression, which can for instance be an analog circuit. If a desired minimum operating pressure, based on a measured pressure imposed in the pneumatic measurement line, proves to be too low, the pressure switch trips an electrical signal, so that the compressed air source begins to supply the requisite demand for compressed air for the consumer. To that end, using a dual-pressure pump or a compressor, for instance, the signal that indicates a demand for compressed air can trip a switch contact for starting up the compressor. In a further feature, the compressed air source itself can be a reservoir from which the demand for compressed air is met. The compressed air reservoir itself is in turn filled with compressed air as needed via a suitable compressor.